Vacuum electric tube



March 10. 1925.

E. Y. ROBINSON VACUUM ELECTRIC TUBE 2 Sheets-Sheet 1 Filed March 21, 1924 |n||| III wIIIIIIIIIIIIIIIIIIII March 10. 19 25.

E. Y. ROBINSON VACUUM ELECTRIC TUBE 2 Sheets-Sheet 2 Filed March 21, 1924 Patented Mar. 10, 1925.

UNITED STATES PATENT oFr1cE- Eamss'r YEOMAN aoBINsoN, or mum-mm, ENGLAND.

vacuum nmzcrmc was.

Application filed March 21, 1924. Serial No. 7 00917."

- it is usual during the process of evacuation to-heat the anode by suitable means such as by thermionic bombardment in order that the anode may be freed of occluded gases and the like. When these vacuum tubes are built in large sizes it is desirable to circulate a cooling fluid round the anode or within the anode in order to cool the said anode. Furthermore, it is also sometimes desirable that a portion of the containing envelope should be metallic, and it is some times arranged that when a portion of the envelope is metallic then this metallic portion serves as the anode and is arranged to be fluid cooled;

As hereinbefore stated it is the practice to heat the anodes and other electrodes of vacuum devices to a high temperature during evacuation in order to get rid of the occluded gases: it is possible to do this because the electrodes are supportedfrom the vitreous container by thin stems, which stems do not conduct heat readily to the vitreous container. Now when the anode is water cooled, or when a portion of the containing envelope is metallic, it is impossible to heat such metallic members to a higher degree than the vitreous container, because the metallic members are in good heat cont-act therewith. In consequence of this, evacuation of the device must be eflected with the metallic electrodes or members at a low temperature. This results in the time of evacu ation being greatly prolonged.

According to this invention means are provided whereby the electrodes or metallic members which may constitute part of the envelope of a vacuum electric tube may be cooled in the neighbourhood of the seal while they are heated to a high temperature over the remainder of their surface. During evacuation of the device, this cooling of. the

electrodes in the nei hbourhood of the seal s preferably effecte "by arranging that a a cool body is in heat contact with the electrodes or members in proximity to'the seal. The cool body may preferably be itself water.

cooled. Moreover, t is preferably arranged that where the electrode is of a metal which oxidizes, such for example as copper or mckel, the heating of the electrodes may be effected in a non-oxidising atmosphere. The

electrode or member may be heated ina reducing atmosphere, such as hydrogen, or in a vacuum; that is to say a vacuum may be' produced on its exterior, the interior of the electrode or member being of course evacuated. The electrode or member may be heated by an electronic bombardment from the cathode or it may be heated by heat radiation from the cathode or from a.

source external to the device or by a combination of these means.

In carrying out the invention as app-lied to a tube having an envelope comprising a metallic anode and vitreous part sealed together, the metallic anode being constructed 1 for example of spun copper, said anode is heated during the evacuation of the tube to a high temperature such as by radiation or by thermionic bombardment from the cathode or by a heater placed external to the 'valve or by inducing high frequency currents in the anode itself'and is cooled in the neighbourhood of the seal between the anode and the vitreous part by means of awater cooled chamber which is in good thermal contact with the anode in proximity to the seal. Alternatively the cooling liquid may be in direct contact with the anode in the neighbourhood of the seal and if desired with the seal itself. 01' a combination of these methods may be employed. The anode may be enclosed in the chamber which may be water jacketed if desired and which is preferably either filled with a reducing or inactive gas which may be at a low pressure chamber may consist of metal or it may consist of an Insulating material when it is desired to heat the anode by inducing high frequency currents therein and it may be of glass or quartz in order to permit the anode being observed during the heating.

The best results are obtained when the chamber is evacuated since in such a case the anode ma be heated to a higher temperature than i gas at say atmospheric pres sure were present as in the latter case the temperature to which the anode may be heated is limited by the fact that it collapses and in the former case the temperature is only limited by the volatilization or meltof the anode.

TVhen the anode is located within the container and is water cooled the invention may be applied in a similar manner and a cooling bod may be inserted in the anode at the point w ere it is sealed tothe vitreous container or within the inlet and outlet cooling pipes of the anode when these latter are the portions whichare sealed to the contalner in order to cool them in proximity to the seal; that is to say, the cooling body is in thermal contact with the anode or the cooling pipes thereof in proximity to the seal and at the surface exterior to theinterior of the valve.

To enable the invention to be clearly understood it will now be described with reference to the accompanying drawin which are sectional elevations illustrating our different arrangements of apparatus in accordance with the invention for use in the removal of gases and vapours from electrodes of vacuum electric tube device.

In these drawings Figure 1 is a side elevation, partly in section, of one embodiment of an apparatus capable of carryin out the present invention, the same being s own applied to a vacuum electric tube.

Fig. 2 is a similar view showing another embodiment of the invention applied to a vacuum electric tube.

Fig. 3 represents in'central vertical section another embodiment of the invention applied to a vacuum electric tube.

- Fig. 4' is a sectional view of another embodiment of the invention applied to a vacuum electric tube of the e in which the angle-is located within thejbnv'elope of the tu Referrin to the drawings the envelope of the valve t erein illustrated consists of the vitreous portionl and a metallic portion 2 for example of copper, which portions are sealed together at 6. The metallic portion 2 constitutes the anode of the device and during the operation thereof is arranged to be water cooled. The anode 2 consisting as it does of a large mass of metal will contain a large quantity of gas and it is essential that this gas should be removed during evacuation of-thedevice. If the means provided in this invention were not employed the anode could not be heated to a temperature much hi her than that to which the seal 6 can safely be heated and thus the permis sible temperature of .the anode when the valve is being evacuated is low, consequently evacuation of the device is a long and expensive process. Now by this invention it is arranged that the anode is heated to a high temperature for the removal of the absorbed lgases and also it is cooled in the neighbour- 00d of the seal. Further, it may be arranged that the exterior df the anode isthe nelghbourhood of the-seal 6, for a purpose which will be explained.

Referring to Fi 1, the anode is cooled in the neighbourhoo the water cooled member 7 which advantageously comprises a rubberichamber and fits on to the conical portion of the anode.

This member is in air tight connection with the metal chamber formed of the tube 3' and the flanged disc 4, an outlet tube 5 being provide The chamber makes an air tight evacuation of the envelope through the tube 21, the anode 2 is heated. In the example shown this'is efiected by supplyin electriwire or the like which is wound .on an inointwith the anode 2 by means of the mem her 7, and the compressing discs 10. During ofits seal by means of V cal energy to a winding 17 of nicke chrome sulating tube 14 of quartz or the like. Lagging 18 is provided between the heater and the casing 3. Electrical connection is made 'to the heater by means of lead-in wires 19 which pass through rubber glands 20. The tube 14 is maintained in position at one end by means of the annular projection 15 on vices such as those shown at 11' and 13, four of which may be provided. Alternatively,- the air tight joint may be made by means of wax or mercury or the like or in the case where the heatin chamber is not evacuated such air tight joint may be omitted. It is 7 preferred that the chamber formed by the members 3 and 4 is evacuated when the thermionic bombardment from the cathode or in those cases in which the gapbetween the anode and the cathode is short the anode may be heated to a sufiiciently high temperature by heat radiated from the cathode.

Referring to the arrangement shown in Fig. '2, the chamber 3 has a cool metal'ring portion 7 one end of which is in thermal contact with the anode 2 of the valve. The chamber 3 is provided with an outlet tube 5 for evacuation and is also provided with a heater in the manner described with reference to Fig 1. An air-tight joint between the-anode 2 and the annular portion 7 is made by means of the rubber gland 22. The'metal body 7 is cooled by means of liquid preferably water which fills the space 23 constituted-by an upward extension of the tube 3. It will be seen that in this case the liquid also cools both the anode in the proximity of the seal and the seal itself. Further, the liquid acts as a sealing liquid and to accentuate the sealing efi'ect the bottom' of the space 23 may be filled with mercur Iii the arrangement illustratedin Fig. 3 the chamber 24 is constructed of quartz or glass for example and is sealed or otherwise fixed to the water cooled member 7 .which is in thermal contact with the anode in the proximity of the seal. The anode of the valve is heated by a thermionic bombardment or heat radiated from the cathode or alternatively it may be heated b inducing high fre uency currents thereln. For this purpose t 1e annular member 7 may be split radially in order to prevent circulating currents being induced therein. A high frequency winding may be arranged outside the chamber 24. An air tight joint between the cooled member 7 .and the chamber 24 and between the member 7 and the anode 2 may be made of wax or the like and the chamber exhausted or alternatively it may merely be covered with a loose packing for example of asbestos and the chamber 24 may be filled with a non-oxidizing gas for example of hydrogen or nitrogen. For this purpose inlet and outlet pipes 25 and 26 are provided.

Referring finally to Fig. 4; which illus trates a cooling arrangement in accordance with the invention applied to a valve in which the anode is located within the vitreous envelope 1 thereof, the latter is provided with two reentrant tubes 27 and 28.

The copper anode 2 which comprises as shown a tube closed at one end is sealed to the figure for the sake of clearness.

may be supported, for example, from the.

the reentrant tube 27. The other electrode or electrodes of the device are'omitted from They lower reentrant tube 28. fThe cathode in one arrangement may comprise a helix of tungsten wiresurrounding the anode ,2.

During the heat treatment ofthe device the anode is heated by means of a thermionic bombardment, for example, and is cooled at the portion 29 thereof which is adjacent the seal 6 by means of the cooled body 7 through which the cooling fluid is circulated. The cooled body 7 is of annular form and to'permit it to. be'inserted within the anode 2 it' comprises two. segmental portlo'ns which are distmct from one another so that the member may be sprung outwards I to press against the inner wall of the anode. The two segments of the cooling member 7 are provided respectively with intake and outlet pipes 30 and 31 and are connected together by a looped tube 32. The tubes 30, 31 and 32 are of suflicient length and sutfie ciently thin to permit the two members 7 being sprung outwards as previously mentioned. The tubes 30 and 31 pass through perforations in the u per end of the chamber 3 and are prefera ly soldered thereto to provide a gas-tight connection therewith. The upper end of the valve envelope 1 is covered by means of a chamber 3 provided with the outlet 5 so that it may be evacuated. An air-tight joint between the chamber 3 and the envelope 1 is obtained by means of a rubber ring 33 which is adapted to be compressed between a clamping ring '10 and the lower end of the chamber 3 by means of the tensioning devices 11 and 13 which are similar to those described in connection with Fig. 1.

The electrode in the neighbourhood of the seal may be cooled by the direct agency of cooling fluid, for example, it may be cooled directly by liquid or it may be cooled by a current of gas which is preferably nonoxidizing, but it is generally preferable to cool it by conduction and convection by contact with a body which is maintained cool by a circulating cooling liquid or medium, as hereinbefore described.

Various modifications may be made without departing from the scope of the invention.

portion of the device and may be of a material more suitable for this purpose; for example it may consist of nickel steel hava coefiicient of expansion approximately equal .to that of the glass employed, and it ma be coated with copper to facilitate the sea g process.

I claim as my invention-- r 1. The step in the method of removing gases and vapors from the metallic rtion of theenvelop'e of a vacuum electric tube,

which metallic envelope portion is welded to a vitreous envelo portion, which consists in heatin sai metallic temperature higher than that which the weld can-withstand to release the gases and vapors from said metallic rtion while substantially conductively vertingthe heat away from that part of the metallic envelope portion in the neighborhood of the weld and then removing the heat thus diverted substantiall by convexion, thus maintaining the weld temperature to protect it. y

2. The method of removing gases and vapors from an electrode whichjs welded to a vitreousportion of the envelo of a vacuum electric tube, which comprises evacuat ing the envelope, and heating said electrode to a temperature substantially h gher than that which the weld can withstand to release the gases and vapors from said electrode while diverting heat from that part of said electrode in the neighborhood of the weld substantially by conduction thro h a body in thermal contact therewith an thenrea moving the diverted heat from said body,

thereby maintaining the weld at a temperature suflicientlylow to protect it.

3. The method of removing gases and vapors from an electrode which comprises the metallic envelope and is sealed to a vitreous portion of the envelope of a vacuum electric tube ofthe metallic container type, which consists in evacuating the interior of the en- 1 velope, maintaining the exterior surfaceof the electrode in an environment substantially free from oxygen, and heating said electrode to a temperature which would be sufiiciently high to cause rapid oxidation in air and is higher than that which the seal can withstand to release the gases and vapors therefrom, while maintaining that artof the electrode which is in the neigh rhood of the seal between the electrode and the vitreous portion of the envelope at a temperature sufliciently lower than that to which the remainder of the electrode is heated to protect the seal.

4. The method of removing gases and vapors from an electrode which comprises the metallic envelope and is sealed to a vitreous portion of the envelope of a vacuum electric tube of the metal container type, which consists in evacuating the interior of portion to a.

at a sufliciently lowthe envelopemaintaining the exterior surface of the electrode in a vacuum, and heatmg said electrode to a temperature which would be sufiiciently high to cause collapsmg thereof if exposed to atmospheric pressure and is'higher than that which the seal can withstand to rapidly release the and vapors therefrom, while maintaining that. art of the electrode which is-in the nu h rhood-of the seal between the elece and the vitreous portion of the envelope at a temperahli'e sufliciently lower than that to which the remainder of the electrode 1s heated to protect the seal.

5. Apparatus for use in the removal of gases and vapors from an electrode which is V sealed to a vitreous portion of the venvelope of a vacuum electric tube, which comprises 7 a fluid-cobled heat-conducting body. having a wall to surround and make thermal contact with the part of the electrode in the neighborhood of the seal, said body being operative to remove heat from said art' of the electrode substantially by con uction through said wall ofthe body.

6. Apparatus for use in the removal,'by heat and evacuation, of gases and vapors from an electrode which is sealed to a vitreous portion of the envelope of a vacuum electric tube and forms part of the envelope thereof, comprising a chamber adapted to enclose the electrode which is to freed from gases and vapors, and a fluid cooled member attached to said chamber and adapted to make thermal contact with said electrode in the region thereof adjacent to the seal whereb heat will be removed from said electrodey conduction through said 'member.

cool said seal, and means for controlling the atmosphere within said chamber. r

8. Apparatus for use in the removal, by heat and evacuation, of gases and vapors from an electrode which is sealed to a vitreous portion of the envelope of a vacuum electric tube and forms part of the envelope thereof, comprising a chamber formed to enclose the electrode which is to be freed from gases and vapors and to make gas-tight connection therewith, means within said chamber for heating the electrode, a fluid-cooled member partly closing one end of said chamber and adapted to make thermal contact 80 chamber and I with the electrode adjacq rit the seal thereof to cool said seal, and means for controlling the atmosphere within said chamber.

9. Ap aratus for use in the removal, by heat ans evacuation, of gases and vapors from an electrode which is sealed to a vitreous portion of the envelope of a vacuum electric tube and forms part of the envelope thereof, com rising a chamber formed to enclose the e ectrode which is to be freed from gases and vapors, an inductive winding within said chamber for heating the electrode by high frequency electric currents, a fluid-cooled member hermetically sealin said chamber and adapted to make therma and hermetically sealing contact with said electrode adjacent the seal thereof to cool the seal, and means for controlling the atmosphere within said chamber. 1

10. Apparatus for use in the removal, by heat and evacuation, of gases and vapors from an electrode which is sealed to a vitreous portion of the envelope of a vacuum electric tube and forms part of the envelope thereof, comprising a chamber formed to en- I close the exterior surface of the electrode, means for producing a removable gas-tightv seal between said chamber and the envelope a tubular body artly closing one end of sai apted to surround and make removable thermal contact with said electrode in the neighborhood of the'seal to cool the seal by conduction, means for permittin the circulation of cooling fluid through sai body, and means for controlling the atmosphere within said chamber.

11. Apparatus for use in the removal, by heat and evacuation, of gases and vapors from an electrode which is 'sealed to a vitreous portion of the envelope of a vacuum electric tube and forms part of the envelope thereof, comprising a chamber formed to en close the exterior surface of the electrode, means for producing a removable gas-tight seal between said chamber and the envelope, a tubular body partly closing one end of said chamber and adapted to surround and make removable thermal contact with said electrode in the neighborhood of the seal to cool the seal by conduction, means for rmitting the circulation of coolin uid through said body, means for contro ing the atmosphere within said chamber, and means located within said chamber for electrically heating the electrode.

I In testimony whereof I have hereunto subscribed my name this 10th day, of March 1924.

ERNEST 'YEOMAN ROBINSON. 

